FIGS. 6 and 7 show a perspective view and a side view of a structure of a prior art infrared ray detection element, and FIG. 8 shows a structure of a prior art infrared ray detector.
In these figures, the reference numeral 2 designates a HgCdTe crystal, the numeral 3 designates an electrode, the numeral 4 designates a light receiving surface, and the reference numeral 1 designates an infrared ray detection element. The reference numeral 5 designates a supporting plate for supporting the infrared ray detection element 1, comprising an electrically insulating material such as sapphire, and the numeral 6 designates an adhesive. The reference numeral 7 designates an adiabatic vacuum vessel (hereinafter referred to as a, "dewar"). The reference numeral 8 designates glass constituting a surrounding wall of the vessel 7, the numeral 9 designates a fernico series alloy on a portion of which the infrared ray detection element 1 is mounted. The reference numeral 10 designates an infrared ray transparent window comprising, for example, ZnS for introducing infrared ray into the vessel 7,. The reference numeral 11 designates a lead wire one end of which is connected to the electrode 3 of the infrared ray detection element 1, and the other end thereof is connected to an electrode lead 27. The reference numeral 12 designates a hollow section for containing a cooling device or medium provided at the center of the dewar 7, and the reference numeral 13 designates an infrared ray detector as described.
The HgCdTe crystal 2 is a compound semiconductor having a small band gap and is widely used as an infrared ray detection element material for detecting infrared rays having wavelengths in the range of 3 to 5 .mu.m or 10 .mu.m.
The HgCdTe crystal 2 is attached to a supporting plate 5 by an adhesive 6, and thereafter the crystal is reduced to a thickness of about 10 .mu.m by grinding or etching,. A material such as indium is vapor plated on the surface, other than the light receiving surface 4, to produce an electrode 3. An anodic oxide film, a protection film such as ZnS film, and a reflection reducing coating or the like are provided on the light receiving surface 4. An infrared ray detection element 1 is fabricated in this way.
The infrared ray detection element 1 is fixed onto the fernico series alloy 9 of the dewar 7 i.e., to a side of the supporting plate 5 with the adhesive 6. Thereafter the air inside of the dewar 7 is exhausted, thereby producing an infrared ray detector 13. The infrared ray detection element 1 is contained in the dewar 7 to enable cooling of the infrared ray detection element 1 down to below 200.degree. K. This cooling of the infrared ray detection element 1 is produced by a cooling device or medium inserted in the hollow section 12 at the center of the dewar 7. A Joule-Thomson cooler, Stirling cycle cooler, Peltier element cooler, or liquid nitrogen may be used as the cooler.
In an infrared ray detector used for detecting a guided missile, the time period from the start of cooling to the start of operation (hereinafter referred to as "cool down time") is required to be short. Actually, a Joule-Thomson cooler is usually used and the cool down time is required to be below several seconds.
Furthermore, although the dewar 7 may be used by exhausting the air therein with a vacuum pump connected thereto, when miniaturization and lightening of the infrared ray detector 13 is required, the sealing of the dewar 7 should be carried out after the inside air is exhausted. At this sealing, air exhaustion is conducted with heating for several tens of hours to maintain the inside of the dewar 7 under vacuum for a long time.
Since it takes a long time for the sealing, it is generally required that the sealing takes place after the evaluation and selection of the infrared ray detection element 1 to aid mass production.
In the prior art infrared ray detector 13, since the thermal conductivities of both the adhesive 6 and the supporting plate 5 are low and the heat capacities thereof are large, the cool down time is disadvantageously long i.e. from 10 several seconds to several minutes.
Furthermore, because it is required to fix the infrared ray detection element 1 to the dewar with the adhesive 6 and connect the wire thereof directly to the electrode 3 in order to evaluate the element characteristics of the infrared ray detection element 1, it is impossible to evaluate and select the infrared ray detection element 1 before sealing the dewar 7. This resulted in poor mass producibility.
An example of another prior art infrared ray detector, is disclosed in Japanese Laid-open Patent Publication No. 57-73637. In this infrared ray detector, an infrared ray detection element may be detachably, mounted on a base plate for provisional mounting of an infrared ray detection element in a dewar.
Another prior art infrared ray detector is disclosed in Japanese Laid-Open Patent Publication No. 57-62569. In this detector, an infrared ray detection element is fixed to a supporting plate having a pin electrode, and thus an infrared detection element may be provisionally mounted in to a dewar.
Another prior art infrared ray detector is described in Japanese Laid-open Patent Publication No. 57-24580. In this detector, an infrared ray detection element is obtained by producing a Hg.sub.1-x Cd.sub.x Te crystal layer on a CdTe substrate by epitaxial growth.